1. Field of the Invention
This invention relates to an opening and closing apparatus for a vehicle window which is mounted in a vehicle such as an automobile or the like and is driven into open and closed positions by a driving source, and to an opening and closing method for the vehicle window in the apparatus.
2. Statement of the Prior Art
Recently, most automobiles are provided with an opening and closing apparatus of a vehicle window known as a power window which employs a motor.
Since power windows can be opened and closed by means of a switch, ease and safety of operation are assured.
However, since the power window or vehicle window is opened and closed under the driving force of a motor, obstacles tend to become trapped between the vehicle and the window frame and leading, on occasion, to serious problems, accident and injury.
For convenience of explanation, a conventional opening and closing apparatus for a vehicle window will be described by referring to FIGS. 12 and 13. FIGS. 12 and 13 show schematic constructions of conventional different opening and closing apparatus for the vehicle window.
One of the conventional opening and closing apparatus, as shown in FIG. 12, includes a current detector 100 which detects a primary current for a motor M driving a vehicle window W and a control section 101 which controls the motor M in accordance with a detecting current from the current detector. In the case that a load is applied to the window W against movement of the window when closing the window W, the current detector 100 detects a surplus current which flows in the motor M and the control section 101 suspends driving of the motor in response to detection of the surplus current.
However, as described above, in the method for detecting the obstacle existing between the vehicle window and the window frame relying on the detection of a surplus current which flows in the motor M, the following problems arise.
First, since the window W is subject to an aging strain due to door impact, a load which is applied to the moving window upon opening and closing the window W is variable. Also, as shown in FIG. 12, a foreign substance A such as dust, small stones or the like tends to become trapped between the window W and side window frames SP. Such foreign substances A cause a load which resists movement of the window W, thereby resulting in a surplus current flow in the motor M. Consequently, if a value of the surplus current at the time of stopping the motor (hereinafter referred to as a setting value) is set to be low, an operation of opening and closing the window W may be stopped by foreign matter trapped between the window W and the side window frame SP.
In order to avoid such a problem, it is necessary to set the setting value to be sufficiently high so as not to cause the motor to stop due to load caused by trapped foreign matter. However, if the setting value is set to be higher, the motor M is not stopped before a substantially long time has lapsed since foreign matter is caught between the window W and an upper window frame UP. Accordingly, the above method suffers from a serious defect.
Another conventional opening and closing control method for a vehicle window which is not subject to the above problem, is as shown in FIG. 13, one in which a light-emitter P and a light-receiver R in a light-detector are mounted on both sides SP of the window W at the opposite positions and the window W can be opened and closed only when the light-receiver R receives a light from the light-emitter P.
However, the light-detector as shown in FIG. 13, suffers from a problem that the relative positions of the light-emitter P and the light-receiver R are not stable and may become misaligned due to a vibration of a vehicle on which they are mounted, thus resulting in light from the light-emitter P failing to reach the light-receiver R, although no obstacle is present. This problems also occurs when the window frame is slightly deformed.